Classifying – separating – and assorting solids – Electrostatic
Reexamination Certificate
2000-07-27
2001-08-07
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Electrostatic
C209S128000
Reexamination Certificate
active
06271492
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a frictional charging device that charges crushed chips of a plurality of kinds of plastics and feeds them to an electrostatic separator used for sorting.
BACKGROUND ART
In recent years, recycling of waste refuse has advanced rapidly. In this connection, plastics consumed as raw material for plastic products are thought to be mostly vinyl chloride type resin (hereinafter referred to as PVC), polyethylene type resin (hereinafter referred to as PE), and polypropylene type resin (hereinafter referred to as PP) and polystyrene type resin (hereinafter referred to as PS) and it is thought that waste plastics that are collected are mostly the aforesaid resins. And when these resins are to be recycled, it is necessary to sort the resins according to kind.
A method for sorting a mixture of chips of said kinds of plastics will now be described with reference to FIG.
14
.
That is, there is a technique in which first, crushed chips
1
of a plurality of kinds of plastics are charged in a frictional charging device
2
. Thereafter, the charged plastic chips
1
are fed from the frictional charging device
2
to an electrostatic separator
3
used for sorting, where particular plastic chips
1
are separated.
Said frictional charging device
2
is in the form of a cylindrical vessel
5
having a loading port
6
formed at one end thereof and a delivery port
7
at the other end. Rotatable stirring vanes (not shown) are installed in said cylindrical vessel
5
, and a loading hopper
8
is installed at said loading port
6
.
Further, said electrostatic separator
3
comprises a metal drum electrode
10
rotatable around a horizontal axis in a predetermined direction, and an arcuate opposed electrode plate
11
extending in the direction of rotation of the metal drum electrode
10
and disposed obliquely above and opposed to the latter. The opposed electrode plate
11
has a negative output of a high voltage source
12
connected thereto, while a positive output of the high voltage source
12
is grounded. As a result of this connection, a rotary grounded electrode is formed on the metal drum electrode
10
and a sorting electrostatic field is formed between the metal drum electrode
10
and the opposed electrode plate
11
.
Disposed below the metal drum electrode
10
are first and second upwardly opened separation vessels
13
and
14
arranged in the order mentioned as seen from upstream of the direction of rotation. Further, disposed on the outer periphery of the metal drum electrode
10
is a brush
15
for scraping off plastic chips
1
sticking to the peripheral surface of the metal drum electrode
10
.
The function of the above arrangement will now be described.
The chips
1
of a plurality of kinds of plastics are loaded through the loading hopper
8
into the cylindrical vessel
5
, where the chips
1
of said kinds of plastics are stirred to be rubbed against each other by the stirring vanes rotating therein, whereby they are frictionally charged. The plastic chips
1
thus charged are delivered from the delivery port
7
and fall onto the metal drum electrode
10
. And the positively charged plastic chips
1
are repelled by the metal drum electrode
10
and drawn toward the opposed electrode plate
11
and fall into the first separation vessel
13
. Further, the negatively charged plastic chips
1
are drawn toward the surface of the metal drum electrode
10
and either fall into the second separation vessel
14
with the rotation of the metal drum electrode
10
or are scraped off the surface of the metal drum electrode
10
by the brush
15
and thereby separated and fall into the second separation vessel
14
.
In the aforesaid sorting of plastic chips
1
, the following has been proposed in order to sort out particular plastic chips
1
with higher accuracy and recover them.
That is, in order that chips
1
of a particular kind of plastic to be sorted out and plastic chips
1
having a reverse polarity to that of said chips
1
of said particular kind of plastic, in the electrification rank for said kinds of plastics forming the chips
1
, may be equal in proportion to each other, particles of either of said plastics should be put as a friction assisting material in the stirring vessel
5
.
For example, if said kinds of plastics forming the chips
1
are PVC, PE, PP, PS, these plastics may be arranged in order of electrification rank as PS→PE→PP→PVC. Here, PS is on the positive side of the electrification rank and PVC is on the negative side of the rank. This shows that PS and PE, when electrified, have a greater amount of positive charge and that PP and PVC, when electrified, have a greater amount of negative charge. Therefore, in the case where, e.g., PVC is to be sorted out, if the amount of PVC is smaller than the total amount of PS and PE, particles of PVC are put as a friction assisting material in the cylindrical vessel
5
such that the amount of PVC is equal to the total amount of PS and PE that are on the positive side of the electrification rank and have a polarity reverse to that of PVC. Further, on the contrary, if the amount of PVC is larger than the total amount of PS and PE, particles of PS and PE that are on the positive side of the electrification rank and have a polarity reverse to that of PVC, are put as a friction assisting material in the cylindrical vessel
5
. Thereby, PVC is sufficiently electrified in a short time to negative polarity, so that PVC can be sorted out with high accuracy in the electrostatic separator
3
.
However, as described above, in the case where the friction assisting material has been put in the cylindrical vessel
5
, the friction assisting material is also delivered through the delivery port
7
of the cylindrical vessel
5
together with the plastic chips
1
, so that there is a problem that a special device is required to recover the delivered friction assisting material and put it back again into the cylindrical vessel
5
.
As a means for solving the above problem, the following arrangement may be contemplated. That is, a friction assisting material
18
of larger particle size than that of plastic chips
1
is used and a net member
16
of orthogonal cross pattern is fixedly attached to the delivery portion
7
of the cylindrical vessel
5
. As shown in
FIGS. 15 and 16
, the meshes
17
of this net member
16
are larger than the plastic chips
1
and smaller than the friction assisting material
18
. The friction assisting material
18
is thus confined in the cylindrical vessel
5
, whereby the friction assisting material
18
can be repetitively used.
In the conventional arrangement described above, however, as shown in
FIG. 15
, even if the meshes
17
of the net member
16
are made larger than the plastic chips
1
, there occurs a problem that such plastic chips
1
are caught by the intersections between the mutually orthogonal wires
16
a
and
16
b
of the net member
16
and gradually clog the meshes
17
of the net member
16
until troubles occur in delivering the charged plastic chips
1
from the delivery port
7
.
Further, as shown in
FIG. 16
, when plastic chips
1
are about to pass through the meshes
17
of the net member
16
for delivery from the delivery port
7
, particles of the friction assisting material
18
traveling to a point just short of the net member
16
together with plastic chips
1
block up the meshes
17
of the net member
16
, presenting a problem that delivery of plastic chips
1
becomes stagnant.
Accordingly, an object of the present invention is provide a frictional charging device wherein a friction assisting material is repetitively used, whereby particular plastic chips are fully charged in a short time and the charged plastic chips can be delivered without any trouble.
DISCLOSURE OF THE INVENTION
The present invention provides a frictional charging device that charges crushed chips of a plurality of kinds of plastics by stirring them and feeds them to an electrostatic separator used for sorting, said friction
Inoue Tetsuya
Maehata Hidehiko
Tamakoshi Daisuke
Tsukahara Masanori
Hitachi Zosen Corporation
Jones David A.
Kusner Mark
Walsh Donald P.
LandOfFree
Frictional charging device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Frictional charging device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Frictional charging device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2516050